The present invention relates to the generation of a gas under pressure within an expansion chamber. Particularly for expelling projectiles, munition or other explosive charges from a container or the like.
Technology involving the blasting of rocks employs hoses filled with pyrotechnic substance. These hoses are known as detonation, explosion or ignition hoses or shot firing cable. Basically they are comprised of a hose made of a synthetic material and being filled with a pyrotechnical substance or having its inner wall coated with a thin continuous layer constituting such a substance. This latter kind of arrangement is known sometimes as ignition hose. The hoses of this type are sealed in one end and being provided with a time delay ignition at the other end. In order to determine the duration of ignition or charge combusion these hoses are usually provided with labels adhesively affixed to the hose and containing information on time interval numbers and the like. Also for holding the coiled hose suitable adhesive ribbons or clamps are provided.
Blasting explosive technique also knows a kind of linear detonation system wherein one or several fuse cords or ignition strands are provided and being held by different layers for example a first synthetic cover upon which is arranged a fiberglass mesh or braid around which in turn another synthetic cover is extruded and this arrangement holds the ignition or fuse cords in position and protects tehm against external effects or interferences. These linear ignition systems are for example used as fuses for gas generators for inflating air bags, igniting rocket drives or as fuse and detonation assists for large size military ordinance.
Military applications are known for example for U.S. Pat. No. 3,865,034. This patent discloses a gas pressure system which is arranged on the inside of a cylindrical casing and is provided for expelling submissiles stored therein. The particular device includes a tubular chamber being perforated by way of ports and being arranged coaxially to the cylindrical casing; the tubular chamber has end covers and extends over the entirety of the stored projectiles or submissiles. Moreover this tubular chamber is provided at a comparatively small caliber. Ignition system for the charge which in turn will cause the gas pressure to be produced. This ignition system is also arranged concentrical to the tubular chamber. The last memtioned charge occupies the annular space between the jacket of the tubular chamber and the ignition device. This ignition device itself is composed of an initiator explosive charge having the configuration of a solid cylinder with a closed area jacket made of an inert material. Moreover a propellant explosive charge is concentrically arranged to the initiator charge and is configured as a hollow cylinder. The ignition device includes furthermore a sleeve for receiving the propellant charge proper and the surrounding initiator charge.
The chamber in which the gas pressure develops on the other hand is enveloped by an expansion chamber having a circular cross section and being provided for cooling of the pressure gases as produced. Just as in the case of the pressure chamber the expansion chamber is configured as a perforated form stable tube and constitutes the outer chamber enclosure. The latter is jacketed by a deformable metal sleeve and a deflatable rubber skin having an internal contour corresponding to the sleeve contour and being provided so that the pressure gas as produced after flowing through the expansion chamber will expell all of the submissiles.
All these known ignition systems for providing a gas pressure have the disadvantage that after ignition of the respective gas producing substance in the respective combustion chamber a certain burn up effect continues which renders difficult the pressure control inside the expansion chamber. That means that the pressure production as it varies in time is difficult to control by the type of ignition system employed whereby particularly it is almost impossible to obtain a stepwise pressure increase. Moreover these ignition systems are inherently rather large which of course means a reduction in payload for a given size of container.